Preliminary preparation of furnace charges for ore-smelting furnaces



Patented Sept, ill, reaa.

barren stares HAWJW rarest caries.

BETHUNE GLASS KLUGH, 0F ANNISTON, ALABAMA, ASSIGNOR TO SOUTHERN MAN-GANESE CORPORATION, OF ANNISTON, ALABAMA, A CORPORATION OF ALABAIEEA.

FBELIMINABY PREPARATION OF FURNACE CHARGES FOR ORE-SMELTING' FUBF NACES.

m Drawing. Application filed June 7, 1918, Serial No. 238,691. RenewedFebruary 15, 1923.

To all whom it may concem:

Be it known that I, Barnum. GLASS KLUGH, a citizen of the United States,residing at Anniston, in the county of Callhoun, Stateof Alabama, haveinvented certain new and useful Improvements in Preliminary Preparationof Furnace Charges for Ore-smelting Furnaces; and I do hereby declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which it.appertains to make and use the same.

The present invention relates to the preliminary preparation of furnacecharges for ore smelting furnaces, and has for its principal object theobtaining of a' preliminary product of such a character that itmay becharged int-o the smelting or reduction furnace 'insuch a condition asto constitute a practically uniform charge, wherein the constituentelements (that is to say the ore reducing material and such fluxes asare pres cut) will be distributed throughout in the appropriateproportions for the smelting or reducing operatlon'intended, andwherein, by reason of the preliminary preparation of the product,certain volatile constituents of the reducing agent employed and thegases" capable of being-driven off by calcination have beenpreliminarily expelled, so that they may not interfere with or delay theprompt beginning and regular progress of the smelting or reduction.

The invention is particularly appropriate for the preparation of furnacecharges for electric smelting furnaces and especially for thepreparation for such furnaces of furnace charges including a carbonateas the ore constituent, as, for instance, carbonate of manganese, whoseadmission as such into the electric furnace is accompanied with certaindisadvantages hereinafter referred to. So also, as will hereinafter morefully appear, the invention supplies a means for minimizing thecorroding effect of the manganese oxides (left after calcination) uponthe furnace electrodes in that to a large extent the manner ofdistribution of the fuel content of the preliminarily prepared chargeshields. the electrodes by carbonaceous coating at those portions of thecharge which are in contact with the electrode surfaces therebycorrespondingly minimizing Broadly considered, the invention consists inintimately interminglingthe ore and its constituent fluxes, in a finelycrushed or ground condition, with carbonaceous material of such acharacter and in such a condi tion as to form with the ore asubstantially homogeneous mixture, and then subjecting the mass(preferably in a'c-losed retort or like chamber from which air is whollyor substantially excluded) to such a temperature as will coke or fritthe mass, and which will incidentally drive off any constituentsvolatile at the temperature employed, which will be in the neighborhoodof a low red heat; (say 500 C. to 575 (3.). So also, any volatileproducts of calcination will be driven off from the ore, together withwhatever moisture is contained in the mass. The product will be of afritted or coke-like character, adapted for immediate use in the oresmelting or reducing furnace, or which may be stored on shipped for suchuse. As hereinbefore pointed out, there may be added to the mass, beforeit is inserted in the distilling and calcining retort or chamber suchappropriate quantity of coke or the like as will determine itsappropriate conductivity for electric furnace uses.

As the'fuel constituent of the mass, I prefer to use pitch from the coaltar, wood tar, or petroleum distillation practice.

Pitch from the coal tar distillation practice, in the form of heavy coal'tar residues, still containing a percentage of bituminous material, isparticularly advantageous, for the reason that it is solid at ordinarytemperatures and can, therefore; be crushed or ground to the same meshas the ore,

thereby facilitating its homogeneous admixture with and distributionthrough the ore, and for the further reason that its melting point isnot far removed from its solidification .point, so that in the veryearly stagesof the heating of the mixture in the distilling retort orchamber, an intimate adhesion of the coal tar pitch and the ore'results,binding the mass together and insuring the production of a homogeneouscoked" product. These properties of coal tar pitch are in part {resentin pitch from the wood tar or petro eum distillation, and even inasphalt, which for some ores and for 'cer- ,tain uses may be employedwith advantage.

I find it desirable and appropriate to crush or grind the ore to suchsize that it' chamber will be provided with connections to a suitablecondensor wherein the solvent may be condensed and recovered for subse:quent use.

The employment of the benzol or like solventpermlts a particularlyintimate and homogeneous distribution of the pitch (and consequently ofthe ultimate carbonaceous residue therefrom) within the mass and as acoating upon each individual particle of the ore.

I may also use, in substitution for, or in addition to the pitch, a richcoking coal of of thebituminous variety, similarly crushed or ground andhavingthe necessary binding qualities. The introduction of coal, in-

stead of or in addition to the pitch has the the function of regulatingthe electric conductivity of the mass and may be employed for thatpurpose either with or without the introduction into the mass of cokeper se.

The heating of the mass inv the retorts or like chambers is proceededwith, under, the conditions hereinbefore'noted, until a coked orfrit'tcd mass is produced. -At the termination of the operation, theretorts or chambers are drawn and the frittedor coke-like product, maybe charged directly. into the smelting or reductionv furnace or, if itis to be used in the electric resistance furnace, of the type whereinthe electrodes, dip into the charge, it may be desirable to first crushor size the product for the electric furnace operation. For the bestresults, it is desirable to so apply the heat to the retorts as toinsure, as far as possible, uniformity of distribution of the heat overthe top, bottom-and sides of .the retorts, thereby insuring acorresponding uniformity in the product. Any suitable form of retort 'orchamber may be employed, dependent upon the character of the ore and.its associated fluxing constituents. In general, iron retorts will befound serviceable for the purpose. a

In the practice of the invention, the operator will find it of advantageto employ that percentage of pitch or its equivalent which will--y1eldthe necessary proportion I of carbon in the coked product for thesmelting or reduction of theamount of ore-present in the coked product.The invention ermits the operator to very carefully adust these relativepercentages, so as to avoid waste of the reducing agent and, therefore,to insure corresponding economy of opera- 'tion. In those instanceswhere the electric conductivity of the furnace charge is to beregulated, the amount of addition and the electric conductivity of theaddition for that purpose can likewise be carefully ascer-,

tained and predetermined. Y

Among the prominent advantages of the invention are that thepredetermined proportioning of the several constituents of'the furnacecharge is accompanied further by thecircumstance that these constituentsare in close contact with each other and are homogeneously distributedthroughout the mass, and that the mass itself is in a co-' herent formof such size and aggregate as is desirable in furnace operations, sothat the" furnace charge maintains its coherence until it is ultimatelydisintegrated by the chemical reactions incident'to the reduction. Thetendency of the materials. of varying sizesand specific gravity tosegregate in the furnace, which is a characteristic defect in the usualsmelting furnace practice and which is productive of decreased output,

lower recovery, and poorer quality of prodnet, is to a large degreeavoided in the use of the present invention. Sov also. as I haveparticularly .pointed out, the diminution in the attack by-theoxygen-bearing constituents of the charge upon the furnace. elec-'trodes, which diminution is a characteristic of the invention, permitsthe use of the electrode-resistance furnace in cases where the usualelectrode consumption would otherwise make the operation commerciallyprohibitive.

I may say further that, in

for the distilling retort or chamber, it may, in some instances, bedesirable, to wet the V reparing at mixture of ore and pitch or :tsequivalent 1' nit mixture, depending u onthe lfind and condition of theore. that the entire charge be weighed and pro- 0 also, it is desirableportioned according to the desired ultimate furnace reactions and thatthe carbonaceous constituent be admixed in such amount as will producethe desired amount of residual" carbon the coked product for the r uiredreaction to be consummated in the e ectrie or other smeltingor reducingfurnace. In some cases, however, the particular. local or commercialconditions prevailing may render it desirable that only a part ofthesmelting charge be treated in accordance with the procem hereindescribed. It will-,.

of course, be understood, that to the extent towhich' such an operation,involves the practice of the inventionfit is to be regarded meme? asincluded within the scope and intent thereof. Furthermore, it will beevident that the volatile products or byproducts from the operationwhich progresses'in the distilling retorts may be collected and saved asan adjunct to the general procedure.

As a particular exemplifica-tion of the practical employment of theprocess, I may specify its application to a form of manganese ores knownmineralogically as rhodochrosite, which is, carbonate of manganese,approximating the chemical formula MnCO The combined carbon dioxide inthis ore is objectionable in smelting operations because the furnaceenergy is wasted in calcining the carbonate, excess of gases escapingthrough the charge, and the carbon dioxide, under the furnace conditionsprevailing, attacks the carbon electrodes. It is, of course, possible todrive off the carbon dioxide by'pre-calcination of the ore, but this isobjectionable not only on account of the expense involved in so doing,but also on account of the disintegration of the ore down to excessivefines. The employment of the present invention, however, permits thecarbon dioxide to be expelled simultaneously with the coking of thepitch or other carbonaceous material and the production of a cokedagglomerate which, when properly sized, is particularly adapted tosmelting or reduc tion in the electric furnace.

The invention is also of notable advantage in the preparation, for usein the elecchemically,

trio reduction furnace, of native manganese oxide ores, manganese oxideore concentrates, by-products consistin in whole or in part of manganeseoxide, and the like, inasmuch as these materials by reason of theircontent of oxygen have, in the ordinary practice, a considerablecorroding effect upon the electrodes, which corroding effect is greatlydecreased by reason of the coating of carbon which the ore articlesreceive when coked or fritted in accordance with the processhereinrdescribed. In fact, in the production of the coke-like mass fromthese materials, a portion of the oxygen combined with the manganese, isremoved by partial reduction, thereby correspondingly relieving theamount of work imposed upon the electric furnace.

Having thus described my invention, what I claim is:

The-method of facilitating the smelting of manganese carbonate ores,which com-'- prises mlxmgthe crushed ore wlth a proportion ofcarbonaceous coking material and simultaneously separating the carbondioxide from the ore and the volatile constituents of the cokingmaterial by subjecting the mixture to a temperature in the neighborhoodof a low red heat, whereby a homogeneous mass suitable for smelting isobtained.

In testimony whereof I 'aflix my signature.

BETHUNE GLASS KLUGH.

